Power operated impact wrench or screwdriver

ABSTRACT

A portable power-operated impact wrench, screwdriver or the like rotary tool, provided with inertia means which causes increased disengagement movement of the hammers from the anvils to interrupt the power to the tool at a predetermined maximum torque by movement of the inertia means in a longitudinal direction of the tool away from the hammers against the action of a compression spring which is adjustable to vary the maximum torque developed by the tool.

United States Patent States June 26, 1973 [54] POWER-OPERATED IMPACTWRENCH 0R 3,387,669 6/1968 Wise, Jr. et a1 173/12 SCREWDRIVER 3,442,3625/1969 Bangerter 173/12 3,515,225 6/1970 States 173/12 [75] Inventor:Ronald Frederick States, London, 3,572,447 3/1971 England 3,578,0915/1971 States 173/12 [73] Assignee: DesoutterBrothersLimited,Hendon,Primary Examiner james A. Leppink London England Attorney-Irving M.Weiner 22 F'led: ul 8 1971 1 1 J y 57 ABSTRACT [21] Appl' 1606o6 Aportable power-operated impact wrench, screwdriver or the like rotarytool, provided with inertia [30] Foreign Application Priority Data meanswhich causes increased disengagement move- Apr. 30, 1971 Great Britain12,319/71 meht 0f the hammers from the ahvils to interrupt the power tothe tool at a predetermined maximum torque 52] U.S. Cl. 173/12, l73/93.6by movement of the inertia means in a longitudinal 51 Int. Cl B251)19/00 reetien of the Keel away from the hammers against the [58] Fieldof Search mm, 93.5, 93.6 eetieh of a compression Spring which isadjustable to vary the maximum torque developed by the tool. [56]References Cited 6 Claims, 7 Drawing Figures UNITED STATES PATENTS3,174,559 3/1965 Vaughn 173/12 3,174,606 3/1965 Honuschanch et a1.173/12 PAIENTEUJUIIZB mm 3.741; 3 1 3 SHEEI=1 0F 4 INVENTOR RONALDFREDERICK STATES M I'ORNEY PAIENTEUauaes 191a 3.741.313

- saw 2 0F 4 INVENYTOR RONALD FREDERIQKSTATES ATTORNEY POWER-OPERATEDIMPACT WRENCH OR SCREWDRIVER The invention relates to portable poweroperated impact wrenches, screwdrivers and like rotary impact tools ofthe kind comprising relatively movable anvil and hammer members withmeans for automatically causing them to become engaged and disengaged asrequired in the operationof the tool, and is an improvement in ormodification of the invention described and claimed in the specificationof British Pat. No. 1180771, which consists in a power-operated impactwrench, screwdriver or like rotary tool of the kind comprisingrelatively movable hammer and anvil members with means for automaticallycausing them to become engaged and disengaged cyclically, characterizedin that there is provided inertia means coupled to the hammer member byresilient means in such manner that, at values of torque below apredetermined value, the inertia means is constrained by the resilientmeans from moving relative to the hammer means, while at thepredetermined value of torque the inertia means moves relative to thehammer means and thereby acts upon the said automatic means to increasethe amount of disengagement movement of the members and operates controlmeans to interrupt a supply of power to the tool.

In the embodiment described and illustrated in the specification of ourBritish Pat. No. 1 180771 the spring means for applying pressure ofpredetermined value to the inertia member is a torsion cylinder withaxial slots in the wall thereof, and it has been found that the torsioncylinder is difficult and expensive to manufacture, and it is thereforeproposed to provide for a linear motion of the inertia means instead ofa rotary motion, thereby making it possible to use a spring whichoperates in a rectilinear manner instead of using a torsion spring.

The invention consists'in a power-operated impact wrench, screwdriver,or like rotary tool as claimed in our British Pat. specification No.1180771, characterized in that the inertia means is supported upon andmoves axially of the hammer member to operate control means to interruptthe supply of power to the tool.

The invention further consists in a power-operated tool as set forth inthe preceding paragraph in which the inertia means is urged in adirection of the hammers by the resilient means to rest upon an abutmentat values of torque below a predetermined value, while at thepredetermined value of torque the inertia means moves away from theabutment against the action of the spring by cam means upon the hammermember and the inertia means.

The invention still further consists in a poweroperated tool as setforth in the preceding paragraph in which the cam means acts to move theinertia means relative to the hammer member due to relative rotationalmovement of the inertia means and the hammer member at the instance ofimpact of the hammers upon the anvils.

The invention still further consists in a poweroperated tool as setforth in the preceding paragraph in which the cam means comprises rampedsurfaces upon the inertia means and the hammer member and a ball betweenand resting upon the ramp surfaces.

The invention still further consists in a poweroperated tool as setforth above in which the resilient means is adjustable to vary themaximum torque developed by the tool.

The accompanying drawings show, by way of example only, one embodimentof the invention in which,

FIG. 1 is a part longitudinal section part elevation of the tool;

FIG. 2 is a section on the line 2-2 of FIG. 1;

FIG. 3 is a section on the line 3--3 of FIG. 1;

FIG. 4 is a section on the line 4-4 of FIG. 1;

FIG. 5 is a section on the line 55 of FIG. 1;

FIG. 6 is a section on the line 6-6 of FIG. 1;

While FIG. 7 is a side elevation of the junction between a relativelongitudinal moving parts of the hammer member.

The tool illustrated is of the pistol grip type, and comprises a motorportion 1, a gear portion 2, a torque control and a hammer and anvilportion 3, a head portion 4 and a pistol grip portion 5.

The motor 6 is of the pneumatic vane type and is of conventional design,the shaft 7 of which is supported in bearings 8 and 9. The shaft 7drives the planetary gears 10, the output of which drives the shaft 11at a reduced speed by way of the enlarged part 12 of the shaft 1 l.

The passage of air from a flexible hose connected to the connector 13 inthe pistol grip portion 5 is controlled by a master valve 14, and passesup the passage 15 to forward direction of push button control valve 16and a reverse direction push button control valve 17, from whence theair passes by channels, not shown, to the appropriate parts of the motor6, to drive it in either direction.

In order that the supply of air to the motor may be interrupted by thetorque control means, hereinafter described, for the forward directionof rotation of the motor and not in the reverse direction of the motor,there is provided a passage 18, connected at the upper end to a pressurerelease valve 19, and at its lower end to the valve 14, and also to therear of the valve 16 by the passage 20. When the pressure release valve19 is opened by the longitudinal movement of the rod 21, then any airunder pressure in the passage 18 is released to atmosphere, and thevalve 14 closes, due to the difference in pressure thus created acrossit, and the motor stops.

The tool holder 22 in the head portion 4 of the tool, is adapted toreceive a wrench, screwdriver or other rotary tool, and is held forrotation in a bearing 23 in the outer casing 24, and is provided with anaxial bore which receives the end 25 of the shaft 11, and is providedwith a thrust ball 26.

The tool holder 22 has a pair of anvils 27 (see also FIG. 2) formedintegral therewith, which are rotatable intermittently when struck bythe continually rotating hammers 28. The hammer members are forconvenience of manufacture constructed in two parts, the outer ring 29carrying the hammers 28, located longitudinally on the inner ring 30 bythe balls 40, but free to move circumferentially thereon for a purposeto be described later.

The inner surface of the inner ring 30 is provided with spiral rampedsurfaces which are engaged by a pair of balls 31, which also engage ingrooves in the surface of the shaft 11, so that, when the hammers 28 areretarded by the anvils 27, the shaft 111, which is continually rotatingurges the balls to roll up the ramps upon the inner ring 30 and urge thelatter in an axial direction of the shaft 11, to compress the helicalspring 32, thereby allowing the hammers 28 to become disengaged from theanvils 27, to pass over them and then re-enter between the anvils torepeat the cycle of operanon.

The ramps on the inner ring 30 and the grooves in the shaft 11 are of aV-shape in elevation, and therefore symmetrical about a plane passingthrough the axis of rotation, and the hammering cycle therefore takesplace in a similar manner in either direction of rotation of the tool.

In order that the pressure relief valve 19 shall be operated when atorque greater than a predetermined maximum is applied by the tool to anut or screw and the motor stopped, an inertia cylinder 33 is keyed tothe inner ring 30 by the keys 34 in the keyway 35, and seeing that theymake a sliding fit therein, the inertia cylinder 33 can movelongitudinally against the action of the dished annular springs 36, butis unable to move circumferentially in relation to the inner ring 30.

The opposed, faces of the ends of the outer ring 29 and the inertiacylinder 33 are provided with conical depressions 37, which each house aball 38, so that, at the instant the hammers strike the anvils, theouter ring 29 is caused to rotate around the inner cylinder 30 to a fewdegrees and due to the action of the balls 38 moves the inertia cylinder33 longitudinally to the inner cylinder 30 and compresses the spring 36.The energy used in compressing springs 36 is returned by theirresilience and the rebound causes the hammer member to move a greaterdistance longitudinally than would be the case for torques below thepredetermined maximum torque. The mass of the inertia cylinder and thestrength of the springs are chosen to fall within the desired range ofmaximum torques to be developed by the tool.

In order for the maximum predetermined torque to be varied, the abutmentmember 39 is movable longitudinally at the inner ring 30 to vary thecompression of the springs 36 by means of a bevel-toothed wheel 41having a screw threaded axial bore 42 on a screw thread on an extension43 of the inner ring 40. The casing 24 is provided with a bore 44through which a tool 45 may be passed and engaged with the teeth on thetoothed wheel 41 to rotate it. The tool is provided with a projectionwhich engages with a small bore 46 in the abutment member 39.

The abutment member 39 is prevented from rotating on the extension 43 ofthe inner ring 29 by a key 48, but which allows longitudinal movementwhen the value of torque is adjusted. The toothed wheel is locked ateach setting by an arcuate spring 49, which is engaged to release it bypressure upon the tool 45 engaged in the bore 47. The bore 44 for thetool is closed by a screw threaded plug 50 when not in use.

The rear end of the extension 43 of the inner ring 30 is provided withan abutment 51 which engages the end of the rod 21 when the inner ringoscillates longitudinally the extra amount caused by the torque reachingthe predetermined level of torque, and pressing upon the ball 19 opensthe valve and stops the motor.

The torque control means only operates in the one direction of rotation,for example, when tightening up a nut, or screw, as it is not necessarywhen the tool rtates in the opposite direction to release a nut orremove a screw.

It can be appreciated from the above description the tool is relativelysimple in form and has few moving parts, which renders it robust, andthat the degree of torque applied by the tool is readily adjustable asto its maximum value.

It is to be understood that the above description is by way of exampleonly, and thatdetails for carrying the invention into effect may bevaried without departing from the scope of the invention claimed.

I claim:

1. In a power-operated impact wrench, screwdriver or like rotary tool ofthe kind comprising relatively movable hammer and anvil members withmeans for automatically causing them to become engaged and disengagedcyclically, and in which there is provided inertia means coupled to thehammer member by resilient means in such manner that, at values oftorque below a predetermined value, the inertia means is constrained bythe resilient means from moving relative to the hammer means, while atthe predetermined value of torque the inertia means moves relative tothe hammer means and thereby acts upon the said automatic means toincrease the amount of disengagement movement of the members andoperates control means to interrupt a supply of power to the tool, theimprovement comprising in that at the values of torque below the saidpredetermined value, the inertia means rests against the hammer memberunder the action of the resilient means, while at the predetenninedvalue of torque, the inertia mans moves away from the hammer memberagainst the action of the resilient means to increase the amount ofdisengagement of the hammer and anvil members.

2. A power-operated tool as claimed in claim 1 in which the hammermember is provided with an abutment against which the inertia memberrests, while the resilient means is a spring which urges the inertiameans against the abutment at values of torque below the saidpredetermined value, while at the predetermined value of torque theinertia means moves away from the abutment by cam means upon the hammermember and the inertia means.

3. A power-operated tool as claimed in claim 2 in which the cam meansacts to move the inertia means away from the hammer member due torelative rotational movement of the hammer member and the inertia meansat the instant of impact of the hammers upon the anvils.

4. A power-operated tool as claimed in claim 3 in which the cam meanscomprises ramped surfaces upon the inertia means and the hammer member,and a ball between and resting upon the ramped surfaces.

5. A power-operated tool as claimed in claim 1 in which the resilientmeans comprises a plurality of dished annular rings mounted coaxial ofthe axis of rotation of the hammer member.

6. A power-operated tool as claimed in claim 5 in which the dishedannular ring remote from the inertia means rests against an abutmentwhich is movable towards and away from the inertia means to adjust theresilient means to vary the predetermined value of

1. In a power-operated impact wrench, screwdriver or like rotary tool ofthe kind comprising relatively movable hammer and anvil members withmeans for automatically causing them to become engaged and disengagedcyclically, and in which there is provided inertia means coupled to thehammer member by resilient means in such manner that, at values oftorque below a predetermined value, the inertia means is constrained bythe resilient means from moving reLative to the hammer means, while atthe predetermined value of torque the inertia means moves relative tothe hammer means and thereby acts upon the said automatic means toincrease the amount of disengagement movement of the members andoperates control means to interrupt a supply of power to the tool, theimprovement comprising in that at the values of torque below the saidpredetermined value, the inertia means rests against the hammer memberunder the action of the resilient means, while at the predeterminedvalue of torque, the inertia mans moves away from the hammer memberagainst the action of the resilient means to increase the amount ofdisengagement of the hammer and anvil members.
 2. A power-operated toolas claimed in claim 1 in which the hammer member is provided with anabutment against which the inertia member rests, while the resilientmeans is a spring which urges the inertia means against the abutment atvalues of torque below the said predetermined value, while at thepredetermined value of torque the inertia means moves away from theabutment by cam means upon the hammer member and the inertia means.
 3. Apower-operated tool as claimed in claim 2 in which the cam means acts tomove the inertia means away from the hammer member due to relativerotational movement of the hammer member and the inertia means at theinstant of impact of the hammers upon the anvils.
 4. A power-operatedtool as claimed in claim 3 in which the cam means comprises rampedsurfaces upon the inertia means and the hammer member, and a ballbetween and resting upon the ramped surfaces.
 5. A power-operated toolas claimed in claim 1 in which the resilient means comprises a pluralityof dished annular rings mounted coaxial of the axis of rotation of thehammer member.
 6. A power-operated tool as claimed in claim 5 in whichthe dished annular ring remote from the inertia means rests against anabutment which is movable towards and away from the inertia means toadjust the resilient means to vary the predetermined value of torque.